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Fig. 1: The R&S RTO oscilloscopes’ outstanding RF
characteristics and their numerous debugging functions for
MIPI interfaces save time during development
(source: Rohde & Schwarz).
Fig. 2: Overview of the MIPI
specifications’ ecosystem
(source: MIPI Alliance).
for display, camera, audio, video,
memory, power management and
interchip communications, for
example, between baseband chips
and those for RF. In addition, it
was adopted as a physical layer
for protocols outside of the MIPI
ecosystem such as Mobile PCIe
(M-PCIe) and SuperSpeed Inter-
Chip (SSIC) USB.
Several higher-level protocols are
specified for each physical layer (Fig.
3). Presently, the variants based on
C-PHY are barely used. The Unified
Protocol (UniPro) specification
makes it possible to use the
similarities for higher-layer protocols
based on M-PHY for interconnecting
components within mobile devices.
The specification is suitable for
a wide range of components
including application processors,
co-processors and modems, as well
as different types of data traffic
including control signals, user data
transfer and packetized streaming.
The Rohde & Schwarz’ R&S RTOs
for example are oscilloscopes which
the user can configure perfectly
for analyzing MIPI interfaces. They
offer different software options for
analyzing MIPI-based protocols and
their respective physical layers (Fig.
4). The following sections describe
how a R&S RTO effectively handles
all T&M requirements of the MIPI
standards. Although both the D-PHY
and M-PHY MIPI standards serve as
examples, the arguments also apply
to the other MIPI options offered by
the R&S RTO.
Detailed analysis of the
physical layer
When analyzing the physical layer, it
is essential to differentiate between
the DUT’s signal integrity and the
signal fidelity of the test equipment.
Critical oscilloscope parameters
include noise, jitter, DC accuracy
and bandwidth limitations at high
amplification factors. The acquisition
of consecutive LP and HS sequences,
which have very different signaling
levels, is particularly challenging.
They require a high signal integrity
in order to determine signal quality
– especially for the HS components.
Fig. 5 shows the respective voltage
levels.
The better the characteristics of
the T&M instrument at hand, the
greater the tolerance range for
the DUT, resulting in cost savings,
lower scrap rates and more efficient
measurements. Thanks to its
excellent features, this is where the
R&S RTO excels – as shown in the
following examples.
Simultaneous acquisition
of 200 mV and 1.2 V
voltages
When characterizing the physical
layer, a full scale of 1.4 V is used
to acquire the LP signal. 8-bit
A/D converters as used in most
oscilloscopes provide a full-scale
resolution of 5.5 mV/bit. While
this is theoretically sufficient for
measurements on the 200 mV signal
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